It is necessary to have a generator in a 5th wheel, I know some have them some don't. We are looking to go to a 5th from our class a and we really don't use ours a lot now.
We have a 2011 Cameo generator ready. Found a used Onan 7000 with a few hours, and dealer installed for me. He did a great job, and muffled out most of the sound. I use it the most to charge batteries during the winter, or if a cold snap comes in after its been unwinterized, I can leave heat on and go start generator every 2-3 days. Really glad I have it. Also use it to run heater or air cond., before we get to RV park.